I have two cartons that I will give away or dispose of. They came with my Tyler Acoustics Taylo Reference Monitors when I bought them used about 12 years ago. We will keep the speakers long-term in our TV area, so no need to keep the boxes around.
Boxes exterior are 14 x 15.5 x 30.5.
Each box has 2 molded endcaps for the 9x10.5 speaker ends. I'm sure that these can be trimmed for larger dimensions.